1. Field of the Invention
This invention is in the field of devices for applying a proper amount of force to each of a large number of medium and large scale integrated circuit (IC) chips and the leads of each chip which IC chips are properly positioned on a multilayer substrate so that such chips and their leads can be reflow soldered to chip pads and chip lead pads of a substrate in a single batch operation.
2. Description of the Prior Art
The prior art known to applicant, relevant to soldering IC chips to a multilayer substrate on which, in some examples, from 50 to 100 such IC chips are soldered has used apparatus which reflow solders one chip and its leads to a substrate at a time. With such prior art devices an operator places a chip and its preformed leads on a chip pad of the substrate so that the back metal layer of the chip overlies the chip pad and the leads of the chip are over the chip lead pads associated with each chip pad. Prior to an IC chip and its leads being reflow soldered to a chip pad and its chip lead pads, all the chip and chip lead pads of a substrate are coated with solder and the solder in turn is coated with a layer of flux. A single force pin applies its weight to only one chip to force the back metal layer of that chip and its leads toward the chip pad and chip lead pads to which the chip and its leads are to be soldered. Radiant energy is concentrated on the area of the substrate occupied by said one chip pad and its associated chip lead pads to melt, or reflow, the solder and cause the solder to wet the back metal layer and the flexible beam leads of the IC chip.
The problem with the prior art apparatus is the time and cost associated with individually placing from 50 to 100 IC chips on a substrate using the prior art apparatus. A skilled operator requires from 60 to 90 minutes to accurately position each IC chip on its chip pad and to reflow solder all of the IC chips to be soldered to a single substrate with the proper degree of reliability and accuracy. As a result, a significant amount of time is required to manufacture each such substrate using prior art apparatus and concommitantly the cost to produce one is also significant.